Heat Exchanger Tube Support

ABSTRACT

A heat exchanger for heat exchange between a first fluid and a second fluid has a plurality of tube sections, each comprising; an interior for passing the first fluid; an exterior for exposure to the second fluid; a first leg; a second leg; a turn joining the first leg to the second leg; and a first face and a second face. A support has at least one carbon member engaging the plurality of tube sections.

BACKGROUND

The disclosure relates to gas turbine engines. More particularly, the disclosure relates to gas turbine engine heat exchangers.

Gas turbine engines (used in propulsion and power applications and broadly inclusive of turbojets, turboprops, turbofans, turboshafts, industrial gas turbines, and the like) include a variety of heat exchangers.

Examples of gas turbine engine heat exchangers are found in: United States Patent Application Publication 20190170445A1 (the '445 publication), McCaffrey, Jun. 6, 2019, “HIGH TEMPERATURE PLATE FIN HEAT EXCHANGER”; United States Patent Application Publication 20190170455A1 (the '455 publication), McCaffrey, Jun. 6, 2019, “HEAT EXCHANGER BELL MOUTH INLET”; and United States Patent Application Publication 20190212074A1 (the '074 publication), Lockwood et al., Jul. 11, 2019, “METHOD FOR MANUFACTURING A CURVED HEAT EXCHANGER USING WEDGE SHAPED SEGMENTS”, the disclosures of which three publications are incorporated by reference in their entireties herein as if set forth at length.

An example positioning of such a heat exchanger provides for the transfer heat from a flow (heat donor flow) diverted from an engine core flow to a bypass flow (heat recipient flow). For example, air is often diverted from the compressor for purposes such as cooling. However, the act of compression heats the air and reduces its cooling effectiveness. Accordingly, the diverted air may be cooled in the heat exchanger to render it more suitable for cooling or other purposes. One particular example draws the heat donor airflow from a diffuser case downstream of the last compressor stage upstream of the combustor. This donor flow transfers heat to a recipient flow which is a portion of the bypass flow. To this end, the heat exchanger may be positioned within a fan duct or other bypass duct. The cooled donor flow is then returned to the engine core (e.g., radially inward through struts) to pass radially inward of the gas path and then be passed rearward for turbine section cooling including the cooling of turbine blades and vanes. The heat exchanger may conform to the bypass duct. The bypass duct is generally annular. Thus, the heat exchanger may occupy a sector of the annulus up to the full annulus.

Other heat exchangers may carry different fluids and be in different locations. For example, instead of rejecting heat to an air flow in a bypass duct, other heat exchangers may absorb heat from a core flow (e.g., as in recuperator use).

Among recently proposed annular heat exchangers are those in United States Patent Application Publication 20150101334A1 (the '334 publication), Bond et al., Apr. 16, 2015, “HEAT EXCHANGERS” and U.S. Pat. No. 10,184,400 (the '400 patent), Cerny et al., Jan. 22, 2019, “Methods of cooling a fluid using an annular heat exchanger”.

SUMMARY

One aspect of the disclosure involves a heat exchanger for heat exchange between a first fluid and a second fluid and comprising a plurality of tube sections. Each tube section has an interior for passing the first fluid; an exterior for exposure to the second fluid; a first leg; a second leg; a turn joining the first leg to the second leg; and a first face and a second face. A support has at least one carbon member engaging the plurality of tube sections.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the at least one carbon member comprises: at least one electrographite carbon (EGC) member

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the at least one carbon member comprises: a first carbon section at the turns along the first faces; a second carbon section at the turns along the second faces; and carbon third sections extending between the first leg and second leg of a respective associated tube section of the plurality of tube sections.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the support is a first support and the heat exchanger comprises a second support spaced from the first support and comprising: a first carbon section along the tube first faces; a second carbon section along the tube second faces; and carbon third sections extending between the first leg and second leg of a respective associated tube section of the plurality of tube sections.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the support is a first support and the heat exchanger comprises a second support spaced from the first support and comprising: at least one carbon member engaging the plurality of tube sections.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the support further comprises a metallic body having: a first section; and a second section joined to the first section to hold the at least one carbon member in at least one stack.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the plurality of tube sections have flattened intermediate portions along their first legs and second legs.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the heat exchanger further comprises: a manifold, wherein the first leg and second leg of each of the tube sections are mounted to the manifold and in communication therewith.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the manifold comprises a plate stack.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the plurality of tube sections are positioned in a plurality of stages from upstream to downstream along a flowpath of the second fluid.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the manifold has a convex outer surface from which the plurality of tube sections extend.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the plurality of tube sections are positioned in a plurality of stages from upstream to downstream along a flowpath of the second fluid.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the at least one carbon member comprises a plurality of members positioned end-to-end in a stage.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, for each tube section the first leg and second leg are spaced transversely to a flowpath of the second fluid.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, for each tube section the first leg and second leg are spaced transversely and streamwise to a flowpath of the second fluid.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, a turbine engine includes the heat exchanger and further comprises a gas path passing gas across exteriors of the plurality of tube sections.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the turbine engine further comprises a recuperator including the heat exchanger.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, a method for using the heat exchanger comprises: passing a first fluid flow through interiors of the tubes; and passing a second fluid flow along a second flowpath across exteriors of the tubes, wherein: the passing of the first flow and the second flow thermally expands the length of the tube sections to cause a sliding interaction between the tubes and the at least one carbon member.

In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the passing the second flow is passing of combustion gases in a gas turbine engine.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of an annular heat exchanger with a small sector shown in solid line and the full annular continuation shown in broken line.

FIG. 1A is a detailed view of the heat exchanger sector of FIG. 1.

FIG. 2 is a front view of the heat exchanger.

FIG. 2A is an enlarged view of a sector of the heat exchanger.

FIG. 2B is an enlarged view of an outer diameter (OD) region of the heat exchanger sector of FIG. 2A.

FIG. 2C is an enlarged view of an inner diameter (ID) region of the heat exchanger sector of FIG. 2A.

FIG. 3 is a partial outer diameter (OD) view of the heat exchanger.

FIG. 4 is a cutaway view of a first type of manifold plate face.

FIG. 5 is a cutaway view of a second form of manifold face.

FIG. 6 is a cutaway outer diameter view of a manifold plate.

FIG. 7 is a cutaway view of a third type of manifold face.

FIG. 8 is a schematic view of a gas turbine engine having the annular heat exchanger in a recuperating supercritical CO₂ bottoming cycle.

FIG. 9 is a transverse sectional view of an alternate heat exchanger.

FIG. 10 is a transverse sectional view of the heat exchanger of FIG. 9.

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG. 1 shows a heat exchanger 20 providing heat exchange between a first flowpath 900 (FIG. 1A) and a second flowpath 902 and thus between their respective first and second fluid flows 910 and 912. In the example embodiment, the flowpaths 900, 902 are gas flowpaths passing respective gas flows 910, 912. In the illustrated example, the first flow 910 enters and exits the heat exchanger 20 as a single piped flow and the flow 912 is an axial annular flow surrounding a central longitudinal axis 500 (FIG. 1) of the heat exchanger. FIG. 1 also shows an axial direction 502 as a generally downstream direction along the second flowpath 902. In a coaxial duct within a gas turbine engine, the axis 500 may be coincident with a centerline of the engine and an axis of rotation of its spools, the direction 502 is an aftward/rearward direction, and a radial direction is shown as 504.

The heat exchanger 20 has a first flow inlet 22 (FIG. 1A) and a first flow outlet 24 along the first flowpath 900. The example inlet and outlet are, respectively, ports of an inlet manifold 26 and an outlet manifold 28. Example manifolds are metallic (e.g., nickel-based superalloy). The inlet manifold and outlet manifold may each have a respective fitting 30A, 30B providing the associated port 22, 24. Each manifold 26, 28 further has a body piece 32A, 32B extending circumferentially about the axis 500 from the associated fitting 30A, 30B and port 22, 24. The example manifolds have continuously curving arcuate form.

The example heat exchanger 20 is a continuous full annulus heat exchanger. An alternative but otherwise similar heat exchanger may be circumferentially segmented into a plurality of segments (e.g., four segments or three to eight segments). Each segment may, itself, be identified as a heat exchanger. Depending upon situation, the segments may be plumbed to have respective first flow 910 segments in parallel, in series, or two totally different first flows.

As is discussed further below, the manifolds 26 and 28 are portions of a larger manifold assembly (manifold) 34 which comprises a stack 36 of plates discussed below in addition to the body pieces 32A, 32B.

A plurality of heat transfer tubes 40 each extend between a first end 42 (FIG. 2C) and a second end 44 at ends of respective legs 46 and 48. Portions of the tubes at the ends 42 and 44 are received in the manifold stack 36. The tubes are bent to be generally U-shaped in planform having respective distal turns 49 (FIG. 2B). The example turns are about 180°. Interiors of the tubes fall along the associated branch of the first flowpath 900 to pass an associated portion of the first flow 910. Central exposed exterior surfaces of the tubes are along the second flowpath 902 in heat exchange relation with the second flow 912.

In the example implementation, the manifold assembly 34 is a combined inlet, outlet, and transfer manifold including the overall heat exchanger inlet and outlet manifolds 26, 28. The transfer manifold function involves transferring from one stage of tubes to the next. In the FIG. 1A example, there are three stages of tubes. The transfer manifolds (and their associated plenums) thus lack immediate external communication. FIG. 1A shows the inlet manifold 26 having an inlet plenum 46A feeding the first legs 46 of the first stage 40A of tubes. A transfer plenum 46B transfers output of the first stage 40A second legs 48 to a transfer plenum 46C which feeds the first legs of the tubes of the second tube stage 40B. A transfer plenum 46D receives the output of the second stage 40B second legs and passes it to a transfer plenum 46E which feeds the third stage 40C first legs. A discharge plenum 46F of the discharge manifold 28 receives the output of the third stage 40C second legs 48 for discharge from the outlet 24.

As is discussed further below, the stack 36 of plates (FIG. 1A) extends between a first axial end 50 and a second axial end 52. Each of the plates has a pair of opposite faces (axially-facing or radially/circumferentially extending), an inner diameter (ID) surface, and an outer diameter (OD) surface. In the example embodiment, the plates are stacked with the aft (downstream along the example second flowpath 902) face of one plate contacting and secured to the forward/upstream face of the next. From upstream-to-downstream along the second flowpath 902 or fore-to-aft in the axial direction 502, the end sections or portions of groups of the tube legs are mounted in pockets 58 (FIG. 1A) formed between the mating plates.

In the example, the tubes of each stage are circumferentially in phase with the tubes of the other stages. However, other configurations may have the tubes of each stage staggered to relative to the adjacent stage(s) to provide out-of-phase registry with the tubes of the adjacent stage fore or aft (e.g., each tube of a given stage is circumferentially directly between two adjacent tubes of each of the two adjacent stages). In the example, the bent tubes have a first face 54 (FIG. 3) and a second face 56 (e.g., facing toward and away from a viewer when viewing the tube as a “U”) with a centerplane 510 parallel to and between the faces. The example plane is at an angle θ relative to a transverse (circumferential in the annular embodiment) direction 506. Example 0 (when not 0° of 180°) is about 45°, more broadly 30° to 60°. Thus, the legs of each tube section are spaced both transverse and streamwise to/along the second flowpath 902.

FIG. 1A shows pockets 58 at the plate junctions accommodating the tube leg end sections. With example circular-section tubing, the pockets 58 are essentially right circular cylindrical pockets split evenly between the two plates and provided by respective semi-cylindrical grooves 90 (FIG. 4) in the two faces. The grooves (or pocket segments/sections) 90 have surfaces 91 and extend between the associated OD surface 100 of a plate on the one hand and a plenum 46A-F discussed above on the other hand.

With the example arcuate manifold configuration, the tubes in each group circumferentially diverge from each other in the radial direction from the manifold assembly 34. Despite this radial fanning arrangement, each group may be identified as a “row” as is common practice with tube-bank heat exchangers. Depending upon implementation, the two legs of each tube may be parallel to each other with the divergence occurring only between adjacent legs of different tubes or the legs of a given tube may slightly diverge. The former (legs of a given tube parallel to each other) may make assembly easier.

The plates of the stack 36 (FIG. 1A) include a first end plate 60, a second end plate 62, and one or more intermediate plates. Depending on implementation, the intermediate plates may be the same as each other or different from each other. In the illustrated example, the intermediate plates are: first and second penultimate plates 64 and 66 respectively adjacent the first and second end plates 60 and 62; and alternating first intermediate plate(s) 68 and second intermediate plate(s) 70.

For full annular heat exchangers there may be a thousand or more tubes per row. Even for a smaller segment of a circumferentially segmented heat exchanger, there may be hundreds of tubes per row or more in the segment. There may be at least an example twenty in a segment (whether stand-alone or assembled with other segments such as sectors discussed above) or a range of twenty to one thousand or twenty to two hundred). An example number of rows is at least two or at least three. Upper limits may be influenced by diminishing return on heat transfer and by increasing fluidic losses along both flowpaths. Thus, an example upper limit on rows is ten with a likely sweet spot of three to six rows.

The manifold 34 has an outer diameter (OD) surface from which the tubes protrude. This outer diameter surface is formed by the combined outer diameter (OD) surfaces 100 (FIG. 4) of the plates (inner diameter (ID) surfaces shown as 102). In the example, the end plates 60 and 62 have flat first end faces forming the axial ends 50 and 52 and second (axially inboard/interior) faces including the groove 90 surfaces 91. FIG. 4 shows such a second face of the end plates 60, 62 having the grooves 90 in an outer diameter section 110 (between intact portions 111 of a planar face) and having a relieved inner diameter section 112. The inner diameter section cooperates (with a similar section of the axially outboard face of the mating penultimate plate 64, 66) to form an annular portion of the associated plenum 46A, 46F in combination with an adjacent annular outwardly-open channel in the inlet or outlet manifold body piece 32A, 32B.

The adjacent face of the respective penultimate plate 64, 66 is similarly configured to and represented by the FIG. 4 illustration. The opposite face (axially inboard) of each penultimate plate 64, 66 has a similar outboard portion 114 (FIG. 5) but an intact inboard portion 116 leaving an intermediate portion forming an annular channel 118 radially therebetween for forming one half of the associated transfer plenum 46B, 46C, 46D, 46E. FIG. 6 shows the intact nature of the section 116 having a face 117 coplanar with intact portions of the outboard portion between the grooves 90.

The first intermediate plates 68 have two faces (FIG. 7) of similar geometry to the penultimate plate 64, 66 inboard faces of FIG. 5 but having an intermediate channel-forming section 130 differing from section 118 by having a plurality of through-holes 132. Through-holes 132 provide transfer from one stage to the next.

The second intermediate plate(s) 70 have both faces similar to the FIG. 5 face and lacking such through-holes 132.

Aerodynamic forces from the second flow 912 as well as other vibrations may cause deleterious resonant behavior in the tubes. Accordingly, it is desirable to support the tubes at one or more radial locations outboard of the manifold 34. FIG. 1A shows an outer diameter support assembly 200 and an intermediate support assembly 202. The number of support assemblies may depend upon numerous factors including the radial span of the tubes.

Each support assembly 200, 202 includes one or more carbon members engaging the tubes. In the illustrated example, each support comprises a stack 204, 206 of carbon blocks. In this example, the OD support 200 has blocks 210, 212, 214, 216, 218, 220, and 222. The intermediate support 202 has blocks 230, 232, 234, 236, 238, 240, and 242. The OD support further includes metallic end plates 224, 226 and the intermediate support includes similar end plates 244, 246. Each support may be axially held together by fasteners 250 such as bolt 252 and nut 254 combinations extending through axial holes in the stack.

FIG. 3 further shows radial straps or struts 260, 262 (e.g., metallic) securing supports 224, 226, 244, 246 to each other and to the manifold 34 to maintain spacing. The example straps may be secured via the fasteners 250 to the associated supports and may be similarly secured to the manifold or may be brazed, welded, or diffusion bonded to the manifold. In alternative embodiments, the straps only connect the supports to each other and not to the manifold and/or may connect to radially outboard environmental structure (e.g., an outer duct wall).

In the annular example, each carbon block includes an inner diameter face, an outer diameter face, and two axial faces. The outboard axial faces of the outboard blocks 210, 222, 230, 242 are flat. The remaining axial faces each have a groove 270 (FIG. 3) as an essentially (semi-circular cylinder) surface 272 and cooperating to form a cylindrical pocket 274 passing the associated tube leg. In this particular example, the grooves in each face of a given block other than the axial end blocks are out of phase with each other. With the angling θ of FIG. 3, portions of three blocks face/contact each face of the tube (e.g., face and contact the tube on one side of the plane 510) and extend between the legs. But only one block extends fully between the legs. FIG. 1A numbers a section 280 of that block between the legs (of block 220 for a tube of the row 40C).

Carbon materials may be the same or similar to those used as high temperature carbon seals. A particular carbon is electrographite carbon (EGC), also known as electrographitic carbon and the like. EGC may made from electrographite which is an artificial graphite manufactured by heating (electrical heating) of another carbon. Electrographite powder may be further processed into EGC end product such as via mixing with a binder and molding/pressing and further heating. Alternatively, the original heating process may leave a net or near net shape component. Non-carbon additives for lubricity, chemical stability (e.g., oxidation) or cohesion may be infiltrated (as “impregnates”) into the component.

The resulting product can survive in the turbine exhaust environment at temperatures of 600° C. Example EGC or other carbon members may be at least of 50% carbon by weight and more particularly closer to commercially pure (e.g., at least 90% or 95% or 99%). The allowable presence of impurities or intended additional elements may depend on particular operational conditions such as temperature and reactive environment.

In use, differential thermal expansion may cause relative sliding of the tubes and carbon blocks. The particular direction of motion may depend on several factors including the temperatures of the fluid flows. EGC offers lubricity for such motion across a wide temperature domain. An example domain may involve peak temperature in the range of 500° C. to 600° C. for placement in a combustion gas flow. When used as an intercooler, temperatures may be about 150° C. In operation, a small amount of graphite/carbon will transfer to the tubes for lubricity. EGC, particularly offers fine grain structure for higher strength and toughness (e.g., resistance to fracture in handling and operation) and higher temperature capability than other graphite carbon materials.

Example tube outer diameters are 1.0 mm to 3.0 mm, more broadly 1.0 mm to 10.0 mm. Example tube radial protrusions (radial span between manifold OD and turn OD) are at least 10 cm, more particularly 10 cm to 50 cm.

Component materials and manufacture techniques and assembly techniques may be otherwise conventional. The tubes may be formed by extrusion or sheet metal rolling techniques, cut to length, and bent to shape. The manifold components may be machined from ingot stock or may be forged and machined or may be cast and machined. Straps and supports may be cut and bent from sheet or strip stock.

Material may be compatible with operational conditions. Example tube, manifold, support, and strap material are stainless steels and nickel-based superalloys.

As noted above, the EGC blocks may be made by pressing pulverized electrographite and binder into a shape (stock shape or possibly a near net shape), heating, impregnating, and machining.

Elements shown as individual pieces may be formed as multiple pieces and then integrated (e.g., via casting annular manifold segments and integrating into a full annulus such as by welding, diffusion bonding, and the like).

The heat exchanger may be assembled in layers starting with a plate at one end of the manifold stack and the associated carbon block(s) at the end(s) of their stack(s). The tubes may be put in place and subsequent layers built up. Depending upon implementation, the tubes may be placed flat atop exposed faces of the plates and blocks or may need to be inserted radially inward.

On stack completion, the bolts 252 or other fasteners (if present) may be inserted through pre-drilled holes (or the fasteners may have been preinstalled and used to help align subsequent blocks during stacking). Nuts 254 may be attached and tightened.

The plates of the manifold may be secured to each other such as via brazing, diffusion bonding, or welding, or may be secured such as by using fasteners as with the bolts.

In some embodiments/uses, the first flow 910 may be a pumped liquid and may remain a pumped liquid. In alternative embodiments/uses, the first flow may be a gas or may start out as a liquid and may be fully or partially vaporized.

An example specific use situation is in a recuperator or waste heat recovery wherein the first flow 910 is of the recuperator working fluid (e.g., carbon dioxide). The heat exchanger 20 may be used as a heat absorption heat exchanger in the hot section of the engine (e.g., absorbing heat from combustion gases (as the second flow 912) in an exhaust duct downstream of the turbine). Alternatively, the heat exchanger may be used as a heat rejection heat exchanger (e.g., rejecting heat to air (as the second flow 912) in a fan duct or other bypass).

FIG. 8 schematically illustrates a gas turbine engine 800, including the heat exchanger 20 in a waste heat recovery system (recuperator) 801. The example engine is an aircraft propulsion engine, namely a turbofan. The engine has a fan section 805, one or more compressor sections 810, a combustor section 820 and one or more turbine sections 830, sequentially along a primary fluid flowpath (core flowpath). The fan also drives air along an outboard bypass flowpath. The example engine is a two-spool engine with the low spool directly or indirectly (e.g., via reduction gearbox) driving the fan. Example combustors are annular combustors and can-type combustor arrays.

A downstream section of the core flowpath provides the second flowpath 902. Downstream of the turbine section 830 is an exhaust casing 840 which exhausts combustion gas (as the fluid flow 912) into an ambient atmosphere downstream of the turbine.

In order to recapture the waste heat from the combustion gas flow 912 and convert the waste heat to work, the heat exchanger 20 is positioned within the exhaust casing 840. The first flowpath 900 is a leg of a supercritical CO₂ (sCO₂) bottoming Brayton cycle (referred to herein as the waste heat recovery system 801). The heat exchanger 20 is connected to transfer heat from the turbine exhaust to the waste heat recovery system 801, and the waste heat recovery system 801 converts the heat into rotational work (which may be used for various purposes such as driving an electrical generator (not shown) to power aircraft systems). The waste heat recovery system 801 may additionally recuperate waste heat within the recovery system 801 and is referred to as a recuperating bottoming cycle.

The waste heat recovery system 801 has a turbine 870 with an inlet 872 connected to an output of the heat exchanger 20. The turbine 870 expands the heated working fluid (CO₂ or other cryogenic fluid 910) and expels the heated working fluid through a turbine outlet 874. The expelled working fluid is passed through a relatively hot passage of a recuperating heat exchanger 880, and is passed to a relatively hot passage of a heat rejection heat exchanger 882. The heat exchanger 882 may be positioned to reject thermal energy from the working fluid to ambient air (e.g., fan bypass air). After passing through the heat rejection heat exchanger 882, the working fluid is passed to an inlet 892 of a compressor 890. The compressor 890 (driven by the turbine 870 (e.g., co-spooled)) compresses the working fluid, and passes the compressed working fluid from a compressor outlet 894 to a cold passage of the recuperating heat exchanger 880.

During operation of the waste heat recovery system 801, the compressor 890 compresses the working fluid, and passes the compressed working fluid through the recuperating heat exchanger 880 and the heat exchanger 20, causing the compressed working fluid to be heated in each of the heat exchangers 20, 880. The heated working fluid is provided to the inlet 872 of the turbine 870 and expanded through the turbine 870, driving the turbine 870 to rotate. The rotation of the turbine 870 drives rotation of the compressor 890 and of an output shaft 802. The output shaft 802 may be mechanically connected to one, or more, additional turbine engine systems and provides work to those systems using any conventional means for transmitting rotational work. Additionally or alternatively, the rotational work can be converted into electricity and used to power one or more engine or aircraft systems using a conventional electrical generator system coupled to the output shaft.

Numerous variations may be implemented. For example, whereas the FIGS. 1-3 heat exchanger is full annulus, the heat exchanger and/or various of its components may be circumferentially segmented. At a minimum, the EGC blocks may be formed as segments of an annulus with each block stage being assembled as a circumferential array of segments. The segments of each sequential stage may be out of phase with each other to improve structural rigidity. The circumferentially segmented EGC block stage may held mounted in annular form by the front and rear plates and/or by mounting to environmental structure.

Although shown with transversely-extending EGC blocks (circumferential in the annular example) other block orientations may be provided including axially-extending (wedge-like blocks in the annular example).

Although each FIG. 1-3 tube is oriented diagonally (e.g., the legs are axially and circumferentially offset from each other) other configurations may involve tubes wherein the legs are not axially offset from each other or not circumferentially offset from each other. That latter example may be particularly amenable to the aforementioned axially-extending alternative block configurations.

Although the example blocks capture portions of the legs leaving the turn protruding out from the associated block(s) alternative examples may involve embedding the turn in the associated block(s). This may be particularly appropriate where the block-to-block boundary extends parallel to the tubes (e.g., the blocks extend circumferentially and are axially stacked where the tube legs of each tube are at the same axial position as each other). In such a situation, to accommodate the differential thermal expansion, the tubes may be accommodated in a broader compartment in the associated block(s).

Although discussed in the context of an annular heat exchanger other configurations are possible. For example, in a rectangular duct a bank of tubes may extend parallel from a straight/flat manifold. Depending upon implementations, there may be two opposite banks extending in opposite directions such as from opposite faces of a single central manifold.

As an example of several such variations, FIGS. 9 and 10 show a heat exchanger 600 that is not full annulus but, extends between ends 602, 604 transverse to the flowpath 902. Additionally, rather than being an arcuate segment (e.g., in a situation where multiple segments are assembled end-to-end to form an annulus) the heat exchanger is straight (e.g., rectangular in footprint looking up or down the flowpath 902). Additionally, the legs of a given tube are spaced purely transversely to the second flowpath 902 rather than at an angle (θ is 0° vs the ˜45° of FIG. 3). FIGS. 9 and 10 show a downstream direction 512 of the flowpath 902, a direction 514 outward from the manifold, and a transverse direction 516 normal thereto.

Even within a given stage, there are multiple discrete blocks end-to-end. FIG. 10 shows a stack of blocks with each block 620 except one axial end block 630 having a plate section 622 and a plurality of protruding portions 624 passing within an associated turn of an associated tube. The end block 630 has only a plate portion. The protrusions 624 have distal ends abutting an adjacent face of an adjacent plate portion. In similar alternative implementations, each face of the plate portion may have a half-height protrusion so that two contacting half-height protrusions form a full-height protrusion to accommodate a tube turn. In the example, the manifold 640 (FIG. 9) has, at each fore-to-aft stage location, a pair of plenums 642, 644 separated from each other by a wall 646. Tube end portions may be of different lengths so that one end portion of each tube is in communication with the first plenum 642 and another in communication with the second plenum 644.

As a further variation, intermediate portions of the tube legs are shown flattened transversely to the flowpath 902 to improve rigidity and aerodynamic stability and increase thermal exposure while limiting restriction of the flow 912. A flattening elongates such intermediate sections of the tubes in the direction of the flowpath 902. If an intermediate support is present, either an adjacent portion of the tube may be undeformed and of circular cross-section or the adjacent face of the blocks may be provided with grooves to accommodate.

FIGS. 9 and 10 show supports, straps, and fasteners similar to those in FIGS. 1-3. Not shown are the overall inlet and outlet ports and plenum-to-plenum transfer apertures similar to those of the FIGS. 1-3 embodiment.

Also, regarding use variations, some variations may have a fuel as the frist fluid flow 910. Although the heat exchanger may transfer heat to a conventional liquid fuel (e.g., kerosene-type jet fuels (such as Jet A, Jet A-1, JP-5, and JP-8), the heat exchanger may be used for future fuels such as liquid hydrogen, potentially vaporizing that fuel.

The use of “first”, “second”, and the like in the following claims is for differentiation within the claim only and does not necessarily indicate relative or absolute importance or temporal order. Similarly, the identification in a claim of one element as “first” (or the like) does not preclude such “first” element from identifying an element that is referred to as “second” (or the like) in another claim or in the description.

Where a measure is given in English units followed by a parenthetical containing SI or other units, the parenthetical's units are a conversion and should not imply a degree of precision not found in the English units.

One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when applied to an existing baseline configuration, details of such baseline may influence details of particular implementations. Accordingly, other embodiments are within the scope of the following claims. 

1. A heat exchanger for heat exchange between a first fluid and a second fluid and comprising: a plurality of tube sections, each comprising: an interior for passing the first fluid; an exterior for exposure to the second fluid; a first leg; a second leg; a turn joining the first leg to the second leg; and a first face and a second face; and a support comprising: at least one carbon member engaging the plurality of tube sections.
 2. The heat exchanger of claim 1 wherein the at least one carbon member comprises: at least one electrographite carbon (EGC) member
 3. The heat exchanger of claim 1 wherein the at least one carbon member comprises: a first carbon section at the turns along the first faces; a second carbon section at the turns along the second faces; and carbon third sections extending between the first leg and second leg of a respective associated tube section of the plurality of tube sections.
 4. The heat exchanger of claim 1 wherein the support is a first support and the heat exchanger comprises a second support spaced from the first support and comprising: a first carbon section along the tube first faces; a second carbon section along the tube second faces; and carbon third sections extending between the first leg and second leg of a respective associated tube section of the plurality of tube sections.
 5. The heat exchanger of claim 1 wherein the support is a first support and the heat exchanger comprises a second support spaced from the first support and comprising: at least one carbon member engaging the plurality of tube sections.
 6. The heat exchanger of claim 1 wherein the support further comprises a metallic body having: a first section; and a second section joined to the first section to hold the at least one carbon member in at least one stack.
 7. The heat exchanger of claim 1 wherein: the plurality of tube sections have flattened intermediate portions along their first legs and second legs.
 8. The heat exchanger of claim 1 further comprising: a manifold, wherein the first leg and second leg of each of the tube sections are mounted to the manifold and in communication therewith.
 9. The heat exchanger of claim 8 wherein: the manifold comprises a plate stack.
 10. The heat exchanger of claim 8 wherein: the plurality of tube sections are positioned in a plurality of stages from upstream to downstream along a flowpath of the second fluid.
 11. The heat exchanger of claim 8 wherein: the manifold has a convex outer surface from which the plurality of tube sections extend.
 12. The heat exchanger of claim 1 wherein: the plurality of tube sections are positioned in a plurality of stages from upstream to downstream along a flowpath of the second fluid.
 13. The heat exchanger of claim 1 wherein: the at least one carbon member comprises a plurality of members positioned end-to-end in a stage.
 14. The heat exchanger of claim 1 wherein for each tube section: the first leg and second leg are spaced transversely to a flowpath of the second fluid.
 15. The heat exchanger of claim 1 wherein for each tube section: the first leg and second leg are spaced transversely and streamwise to a flowpath of the second fluid.
 16. A turbine engine including the heat exchanger of claim 1 and further comprising: a gas path passing gas across exteriors of the plurality of tube sections.
 17. The turbine engine of claim 16 further comprising: a recuperator including the heat exchanger.
 18. A method for using the heat exchanger of claim 1, the method comprising: passing a first fluid flow through interiors of the tube section; and passing a second fluid flow along a second flowpath across exteriors of the tube sections, wherein: the passing of the first flow and the second flow thermally expands the length of the tube sections to cause a sliding interaction between the tube sections and the at least one carbon member.
 19. The method of claim 18 wherein: the passing the second flow is passing of combustion gases in a gas turbine engine. 